резервная копия журналов(A backup of transaction logs that includes all log records not backed up in previous log backups. Log backups are required under the full and bulk-logged recovery models and are unavailable under the simple recovery model)
резервная копия заключительного фрагмента журнала(A log backup taken from a possibly damaged database to capture the log that has not yet been backed up. A tail-log backup is taken after a failure in order to prevent work loss)